U.S. patent number 11,190,367 [Application Number 16/830,864] was granted by the patent office on 2021-11-30 for multicast forwarding method and multicast router.
This patent grant is currently assigned to HUAWEI TECHNOLOGIES CO., LTD.. The grantee listed for this patent is HUAWEI TECHNOLOGIES CO., LTD.. Invention is credited to Yong Huang, Rui Meng, Chuang Wang.
United States Patent |
11,190,367 |
Meng , et al. |
November 30, 2021 |
Multicast forwarding method and multicast router
Abstract
This application discloses a multicast forwarding method and a
multicast router. The method includes: listening to, by a first
multicast router, a plurality of unicast packets passing through
the first multicast router, and determining a set of unicast
packets that are from a same upstream multicast router and that
belong to a same unicast stream; when determining that destination
addresses of at least two unicast packets in the unicast packet set
are different, sending, by the first multicast router, a prune
message to the upstream multicast router; and sending, by the first
multicast router, the received unicast packets with the multicast
identifier to the destination devices corresponding to the
destination address group. The method is used to provide a new
multicast method, so as to implement multicast functions of some
routers in an existing unicast network architecture.
Inventors: |
Meng; Rui (Beijing,
CN), Wang; Chuang (Beijing, CN), Huang;
Yong (Shenzhen, CN) |
Applicant: |
Name |
City |
State |
Country |
Type |
HUAWEI TECHNOLOGIES CO., LTD. |
Guangdong |
N/A |
CN |
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Assignee: |
HUAWEI TECHNOLOGIES CO., LTD.
(Guangdong, CN)
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Family
ID: |
1000005965858 |
Appl.
No.: |
16/830,864 |
Filed: |
March 26, 2020 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20200228356 A1 |
Jul 16, 2020 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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PCT/CN2018/104423 |
Sep 6, 2018 |
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Foreign Application Priority Data
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Sep 27, 2017 [CN] |
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201710892283.9 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L
12/18 (20130101); H04L 45/74 (20130101) |
Current International
Class: |
H04L
12/18 (20060101); H04L 12/741 (20130101) |
References Cited
[Referenced By]
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WO |
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Other References
B Fenner: Protocol Independent Multicast--Sparse Mode (PIM-SM):
Protocol Specification (Revised), RFC7761, Mar. 2016, total 137
pages. cited by applicant.
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Primary Examiner: Oveissi; Mansour
Attorney, Agent or Firm: Womble Bond Dickinson (US) LLP
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation of International Application No.
PCT/CN2018/104423, filed on Sep. 6, 2018, which claims priority to
Chinese Patent Application No. 201710892283.9, filed on Sep. 27,
2017. The disclosures of the aforementioned applications are hereby
incorporated by reference in their entireties.
Claims
What is claimed is:
1. A multicast forwarding method comprising: listening to, by a
first multicast router, a plurality of unicast packets passing
through the first multicast router; determining a set of unicast
packets that are from a same upstream multicast router and that
belong to a same unicast stream, wherein the unicast packets in the
unicast stream carry a same multicast identifier, and the multicast
identifier indicates that the unicast packets in the unicast stream
are from a same data source server and are to be sent to
destination devices that belong to a same multicast group; when
determining that destination addresses of at least two unicast
packets in the unicast packet set are different, sending, by the
first multicast router, a prune message to the upstream multicast
router, wherein the prune message carries a destination address
group determined from all the unicast packets in the unicast packet
set, the prune message used to instruct the upstream multicast
router to stop sending the unicast packets with the multicast
identifier to the destination devices corresponding to the
destination address group, and send the to-be-sent unicast packets
with the multicast identifier to the first multicast router; and
sending, by the first multicast router, the received unicast
packets with the multicast identifier to the destination devices
corresponding to the destination address group.
2. The method according to claim 1, wherein the method further
comprises: when determining that destination addresses of at least
two unicast packets in the unicast packet set are different,
obtaining, by the first multicast router, destination addresses of
all packets in the unicast packet set, and generating a first
multicast routing entry, wherein a source address of the first
multicast routing entry is an address of the first multicast
router, and the destination address group comprises all the
destination addresses; and the sending, by the first multicast
router, the received unicast packets with the multicast identifier
to the destination devices corresponding to the destination address
group comprises: modifying, by the first multicast router, the
received unicast packet with the multicast identifier based on the
first multicast routing entry, to obtain a modified unicast packet,
wherein a source address of the modified unicast packet is the
address of the first multicast router, and a destination address of
the modified unicast packet is a destination address in the
destination address group and in the first multicast routing entry;
and sending, by the first multicast router, the modified unicast
packet to the destination devices corresponding to the destination
address group.
3. The method according to claim 2, further comprising: obtaining,
by the first multicast router through listening, a first message
sent by the upstream multicast router, wherein the first message
carries the multicast identifier and a first target address, and is
used to indicate that a destination device corresponding to the
first target address stops receiving a unicast packet with the
multicast identifier; searching, by the first multicast router, for
the first multicast routing entry corresponding to the multicast
identifier, and determining that the first target address belongs
to the destination address group; and removing, by the first
multicast router, the first target address from the first multicast
routing entry, and stopping sending the unicast packet with the
multicast identifier to the destination device corresponding to the
first target address.
4. The method according to claim 3, further comprising:
determining, by the first multicast router, that a destination
address in the first multicast routing entry from which the first
target address is removed is empty; and instructing, by the first
multicast router, the upstream multicast router to stop sending the
unicast packet with the multicast identifier to the first multicast
router.
5. A multicast forwarding method comprising: receiving, by a second
multicast router, a prune message from a downstream multicast
router, wherein the prune message comprises a destination address
group determined by the downstream multicast router from all
unicast packets in a unicast packet set, the unicast packet set is
a set of unicast packets that are obtained by the downstream
multicast router by listening to a plurality of unicast packets
passing through the downstream multicast router that are from the
second multicast router, and that belong to a same unicast stream,
a unicast packet in the unicast stream carries a multicast
identifier, and the multicast identifier indicates that the unicast
packets in the unicast stream are from a same data source server
and are to be sent to destination devices that belong to a same
multicast group; and stopping, by the second multicast router based
on the prune message, sending the unicast packets with the
multicast identifier to the destination devices corresponding to
the destination address group, and sending the to-be-sent unicast
packets with the multicast identifier to the downstream multicast
router.
6. The method according to claim 5, before the receiving, by a
second multicast router, a prune message from a downstream
multicast router, further comprising: receiving, by the second
multicast router, a registration request from the data source
server, wherein the registration request carries IP four-tuple
information of a User Datagram Protocol (UDP) session; allocating,
by the second multicast router, a multicast group identifier to the
UDP session based on the registration request; sending, by the
second multicast router, a registration request response message to
the data source server, wherein the response message carries the
multicast group identifier; and receiving, by the second multicast
router, a unicast packet sent by the data source server, wherein a
header of the unicast packet carries the multicast identifier, and
the multicast identifier is generated by the data source server
based on an address of the data source server and the multicast
group identifier.
7. The method according to claim 6, further comprising: receiving,
by the second multicast router, an on-demand request from a first
client, wherein the on-demand request is used to request to
subscribe to the UDP session; and generating, by the second
multicast router, a second multicast routing entry, wherein a
source address of the second multicast routing entry is an address
of the second multicast router, and a destination address of the
second multicast routing entry is an address of the first client;
and the sending, by the second multicast router, a to-be-sent
unicast packet with the multicast identifier to the downstream
multicast router comprises: modifying, by the second multicast
router, the received unicast packet with the multicast identifier
based on the second multicast routing entry, to obtain a modified
unicast packet, wherein a source address of the modified unicast
packet is the address of the second multicast router, and a
destination address of the modified unicast packet is the address
of the first client; and sending, by the second multicast router,
the modified unicast packet with the multicast identifier to the
first client.
8. The method according to claim 7, further comprising: receiving,
by the second multicast router, an on-demand stop request sent by
the first client, wherein the on-demand stop request is used to
request to stop subscribing to the UDP session; searching, by the
second multicast router, for the second multicast routing entry
corresponding to the multicast identifier, and determining that the
address of the first client is comprised in the destination address
of the second multicast routing entry; and removing, by the second
multicast router, the address of the first client from the second
multicast routing entry, and stopping sending the unicast packet
with the multicast identifier to a destination device corresponding
to the address of the first client.
9. The method according to claim 7, further comprising: searching,
by the second multicast router, for the second multicast routing
entry corresponding to the multicast identifier, and determining
that the address of the first client is not included in the
destination address of the second multicast routing entry;
generating, by the second multicast router, a first message based
on the second multicast routing entry, wherein a source address of
the first message is the address of the second multicast router, a
destination address of the first message is the address of the
first client, and the first message carries the multicast
identifier, and is used to notify the downstream multicast router
that a destination device corresponding to the first target address
stops receiving a unicast packet with the multicast identifier; and
sending, by the second multicast router, the first message to the
first client, so that the downstream multicast router stops, after
obtaining the first message through listening, sending the unicast
packet with the multicast identifier to the first client.
10. A multicast router comprising: a communications interface; a
processor; and a memory, wherein the processor executes an
instruction stored in the memory, to perform operations comprising:
listening to, by using the communications interface, a plurality of
unicast packets passing through the processor, and determining a
set of unicast packets that are from a same upstream multicast
router and that belong to a same unicast stream, wherein the
unicast packets in the unicast stream carry a same multicast
identifier, and the multicast identifier indicates that the unicast
packets in the unicast stream are from a same data source server
and are to be sent to destination devices that belong to a same
multicast group; when determining that destination addresses of at
least two unicast packets in the unicast packet set are different,
sending a prune message to the upstream multicast router by using
the communications interface, wherein the prune message carries a
destination address group determined from all the unicast packets
in the unicast packet set, the prune message used to instruct the
upstream multicast router to stop sending the unicast packets with
the multicast identifier to the destination devices corresponding
to the destination address group, and send the to-be-sent unicast
packets with the multicast identifier to the first multicast
router; and sending, by using the communications interface, the
received unicast packets with the multicast identifier to the
destination devices corresponding to the destination address
group.
11. The multicast router according to claim 10, wherein the
processor is further configured to: obtain destination addresses of
all packets in the unicast packet set, and generate a first
multicast routing entry, wherein a source address of the first
multicast routing entry is an address of the first multicast
router, and the destination address group comprises all the
destination addresses; modify the received unicast packet with the
multicast identifier based on the first multicast routing entry, to
obtain a modified unicast packet, wherein a source address of the
modified unicast packet is the address of the first multicast
router, and a destination address of the modified unicast packet is
a destination address in the destination address group and in the
first multicast routing entry; and send, by using the
communications interface, the modified unicast packet to the
destination devices corresponding to the destination address
group.
12. The multicast router according to claim 11, wherein the
processor is further configured to: obtain, through listening by
using the communications interface, a first message sent by the
upstream multicast router, wherein the first message carries the
multicast identifier and a first target address, and is used to
indicate that a destination device corresponding to the first
target address stops receiving a unicast packet with the multicast
identifier; search for the first multicast routing entry
corresponding to the multicast identifier, and determine that the
first target address belongs to the destination address group; and
remove the first target address from the first multicast routing
entry, and stop sending the unicast packet with the multicast
identifier to the destination device corresponding to the first
target address.
13. The multicast router according to claim 12, wherein the
processor is further configured to: determine that a destination
address in the first multicast routing entry from which the first
target address is removed is empty; and instruct, by using the
communications interface, the upstream multicast router to stop
sending the unicast packet with the multicast identifier to the
processor.
Description
TECHNICAL FIELD
This application relates to the field of information technologies,
and in particular, to a multicast forwarding method and a multicast
router.
BACKGROUND
An implementation of Internet Protocol (IP) network communication
is unicast, which is characterized by transmitting one message to
one receiver once; and another implementation is broadcast, which
is characterized by transmitting one message to all receivers in a
subnet once. When there are a plurality of receivers in a network,
the unicast manner may cause generation of a plurality of copies of
a same message in the IP network, and a network resource and a
server resource are repeatedly occupied. Consequently, transmission
efficiency is low. However, different subnets cannot be covered in
the broadcast manner. Otherwise, a broadcast storm is triggered.
Therefore, a multicast transmission mode of "transmitting one
message to a plurality of receivers once" emerges.
IP multicast means that a multicast routing entry is established
between a receive end and a multicast source hop by hop by using a
multicast routing protocol, and a tree-like structure (namely, a
multicast distribution tree) using the multicast source as a root
and using a receive end as a leaf is finally constructed. A
multicast packet is copied on each multicast router from the root
node to the leaf, and ends at a terminal. The Protocol Independent
Multicast-Sparse Mode (PIM-SM) Protocol is a multicast routing
protocol currently well recognized. However, the PIM-SM protocol
still has various disadvantages. For example, all routers in an IP
multicast network need to support the PIM-SM protocol, and once a
router that is running the PIM-SM breaks down, a multicast service
of a terminal connected to a branch tree of the router cannot be
automatically recovered.
SUMMARY
In view of this, this application provides a multicast forwarding
method and a multicast router, so as to provide a new multicast
method, thereby implementing multicast functions of some routers in
an existing unicast network architecture.
According to a first aspect, an embodiment of this application
provides a multicast forwarding method, and the method includes:
listening to, by a first multicast router, a plurality of unicast
packets passing through the first multicast router, and determining
a set of unicast packets that are from a same upstream multicast
router and that belong to a same unicast stream; when determining
that destination addresses of at least two unicast packets in the
unicast packet set are different, sending, by the first multicast
router, a prune message to the upstream multicast router; and
sending, by the first multicast router, a received unicast packet
with the multicast identifier to destination devices corresponding
to the destination address group.
An objective of this method is: Once a multicast router on a branch
tree of a communications network finds, through listening, that
destination addresses of unicast packets in the unicast packet set
are different, a plurality of same unicast streams corresponding to
different destination addresses are combined. In other words, the
upstream multicast router is instructed to no longer send the
plurality of same unicast streams but send only one unicast stream
to a downstream multicast router, and the downstream multicast
router distributes the unicast stream to destination devices
corresponding to the different destination addresses. Therefore, a
multicast function can be implemented in a network when some
devices support multicast. In addition, some same unicast streams
may be combined when the multicast function is implemented, thereby
reducing network bandwidth consumption.
In one embodiment, when the first multicast router determines that
destination addresses of at least two unicast packets in the
unicast packet set are different, the first multicast router
obtains destination addresses of all packets in the unicast packet
set, and generates a first multicast routing entry. A source
address of the first multicast routing entry is an address of the
first multicast router, and the destination address group includes
all the destination addresses. In this way, the first multicast
router can maintain access or departure of a downstream destination
terminal by using the multicast routing entry, to manage a
client.
In one embodiment, after the first multicast router generates the
multicast routing entry, the first multicast router modifies the
received unicast packet with the multicast identifier based on the
first multicast routing entry, to obtain a modified unicast packet,
and then sends the modified unicast packet to the destination
devices corresponding to the destination address group.
A source address of the modified unicast packet is the address of
the first multicast router, and a destination address of the
modified unicast packet is a destination address in the destination
address group and in the first multicast routing entry, so that the
first multicast router may distribute, based on the first multicast
routing entry, a unicast stream combined by the upstream to
different destination devices, thereby implementing the multicast
function.
In one embodiment, the first multicast router obtains, through
listening, a first message sent by the upstream multicast router,
where the first message carries the multicast identifier and a
first target address, and is used to indicate that a destination
device corresponding to the first target address stops receiving a
unicast packet with the multicast identifier.
The first multicast router searches for the first multicast routing
entry corresponding to the multicast identifier, and determines
that the first target address belongs to the destination address
group. The first multicast router removes the first target address
from the first multicast routing entry, and stops sending the
unicast packet with the multicast identifier to the destination
device corresponding to the first target address.
In other words, once obtaining, through listening, an instruction
message from an upstream for stopping packet forwarding, the
multicast router on the branch tree searches for a multicast
routing entry of the multicast router according to a specified
rule, so as to remove the destination device from the multicast
routing entry. Because the multicast routing entry does not include
the destination address, the multicast router stops sending a
unicast packet to the destination device.
In another case, assuming that a destination address list is empty
after the first multicast router removes a first destination
address from the multicast routing entry, the first multicast
router instructs the upstream multicast router to stop sending the
unicast packet with the multicast identifier to the first multicast
router. In other words, if a downstream branch of the first
multicast router does not have a destination device that is to
forward a packet, an upstream branch does not directly send the
combined unicast stream to the first multicast router.
According to a second aspect, an embodiment of this application
provides a multicast forwarding method, and the method includes:
receiving, by a second multicast router, a prune message from a
downstream multicast router; and stopping, by the second multicast
router based on the prune message, sending unicast packets with the
multicast identifier to destination devices corresponding to the
destination address group, and sending the to-be-sent unicast
packets with the multicast identifier to the downstream multicast
router.
The prune message includes a destination address group determined
by the downstream multicast router from all unicast packets in a
unicast packet set, the unicast packet set is a set of unicast
packets that are obtained by the downstream multicast router by
listening to a plurality of unicast packets passing through the
downstream multicast router, that are from the second multicast
router, and that belong to a same unicast stream, a unicast packet
in the unicast stream carries a multicast identifier, and the
multicast identifier indicates that the unicast packets in the
unicast stream are from a same data source server and are to be
sent to destination devices that belong to a same multicast group.
Therefore, the second multicast router may combine unicast streams
corresponding to the destination address group after receiving the
prune message, and therefore only needs to send a combined unicast
stream to the downstream multicast router, so as to reduce network
bandwidth consumption.
In one embodiment, the second multicast router receives a
registration request from the data source server, where the
registration request carries IP four-tuple information of a User
Datagram Protocol (UDP) session. The second multicast router
allocates a multicast group identifier to the UDP session based on
the registration request.
The second multicast router sends a registration request response
message to the data source server, where the response message
carries the multicast group identifier. The second multicast router
receives a unicast packet sent by the data source server, where a
header of the unicast packet carries the multicast identifier, and
the multicast identifier is generated by the data source server
based on an address of the data source server and the multicast
group identifier.
In other words, the second multicast router further has a function
of allocating a multicast identifier to the UDP session of the data
source server. In this way, the data source server inserts the
multicast identifier into packets, to indicate that the packets are
from a same data source and are of a same type, and send the
packets to the destination devices of the same multicast group, so
that the downstream multicast router listens to the packets, and
identifies unicast streams that can be combined.
In one embodiment, the second multicast router receives an
on-demand request from a first client, where the on-demand request
is used to request to subscribe to the UDP session. The second
multicast router generates a second multicast routing entry, where
a source address of the second multicast routing entry is an
address of the second multicast router, and a destination address
of the second multicast routing entry is an address of the first
client. In this way, the second multicast router can maintain
access and departure of each terminal device, so as to facilitate
charging management.
In one embodiment, the second multicast router modifies the
received unicast packet with the multicast identifier based on the
second multicast routing entry, to obtain a modified unicast
packet, where a source address of the modified unicast packet is
the address of the second multicast router, and a destination
address of the modified unicast packet is the address of the first
client. The second multicast router sends the modified unicast
packet with the multicast identifier to the first client. The
second multicast router modifies the unicast packet, and the
modified unicast packet is a multicast packet, so that a multicast
function can be implemented.
In one embodiment, the second multicast router receives an
on-demand stop request sent by the first client, where the
on-demand stop request is used to request to stop subscribing to
the UDP session. The second multicast router searches for the
second multicast routing entry corresponding to the multicast
identifier, and determines that the address of the first client is
included in the destination address of the second multicast routing
entry.
The second multicast router removes the address of the first client
from the second multicast routing entry, and stops sending the
unicast packet with the multicast identifier to a destination
device corresponding to the address of the first client.
In other words, once receiving the on-demand stop request sent by a
client, the second multicast router searches for a multicast
routing entry of the second multicast router. If the multicast
routing entry exists and the address of the client is in a
destination address list, the second multicast router removes the
multicast routing entry from the destination address, and
subsequently a packet is not sent to the client.
In one embodiment, the second multicast router searches for the
second multicast routing entry corresponding to the multicast
identifier, and determines that the address of the first client is
not included in the destination address of the second multicast
routing entry. The second multicast router generates a first
message based on the second multicast routing entry, where a source
address of the first message is the address of the second multicast
router, a destination address of the first message is the address
of the first client, and the first message carries the multicast
identifier, and is used to notify the downstream multicast router
that a destination device corresponding to the first target address
stops receiving a unicast packet with the multicast identifier. The
second multicast router sends the first message to the downstream
multicast router, so that the downstream multicast router stops,
after obtaining the first message through listening, sending the
unicast packet with the multicast identifier to the first
client.
In other words, when determining that a first destination address
is not in the multicast routing entry of the second multicast
router, the second multicast router sends the first message to the
downstream multicast router. In other words, the downstream
multicast router is instructed to perform searching, and stop
sending a packet to the client.
According to a third aspect, an embodiment of this application
further provides a multicast forwarding apparatus, and the
apparatus has functions of implementing behavior of a terminal in
the method example of the foregoing first aspect. The functions may
be implemented by hardware, or may be implemented by hardware by
executing corresponding software. The hardware or the software
includes one or more modules corresponding to the foregoing
functions. In one embodiment, the apparatus includes a listening
unit, a determining unit, a sending unit, a receiving unit, and a
first multicast router of a method side corresponding to the
apparatus. The listening unit is configured to listen to a
plurality of unicast packets passing through the listening unit.
The determining unit is configured to determine a set of unicast
packets that are from a same upstream multicast router and that
belong to a same unicast stream, where the unicast packets in the
unicast stream carry a same multicast identifier, and the multicast
identifier indicates that the unicast packets in the unicast stream
are from a same data source server and are to be sent to
destination devices that belong to a same multicast group. The
sending unit is configured to: when determining that destination
addresses of at least two unicast packets in the unicast packet set
are different, send a prune message to the upstream multicast
router, where the prune message carries a destination address group
determined from all the unicast packets in the unicast packet set,
the prune message is used to instruct the upstream multicast router
to stop sending the unicast packets with the multicast identifier
to the destination devices corresponding to the destination address
group, and send the to-be-sent unicast packets with the multicast
identifier to the first multicast router. The sending unit is
configured to send the unicast packet with the multicast identifier
received by the receiving unit to the destination devices
corresponding to the destination address group.
In one embodiment, the multicast forwarding apparatus further
includes a generation unit, configured to obtain destination
addresses of all packets in the unicast packet set, and generate a
first multicast routing entry, where a source address of the first
multicast routing entry is an address of the first multicast
router, and the destination address group includes all the
destination addresses.
In one embodiment, the multicast forwarding apparatus further
includes a processing unit, configured to: modify the received
unicast packet with the multicast identifier based on the first
multicast routing entry, to obtain a modified unicast packet, where
a source address of the modified unicast packet is the address of
the first multicast router, and a destination address of the
modified unicast packet is a destination address in the destination
address group and in the first multicast routing entry; and send
the modified unicast packet to the destination devices
corresponding to the destination address group.
In one embodiment, the listening unit is further configured to
obtain, through listening, a first message sent by the upstream
multicast router, where the first message carries the multicast
identifier and a first target address, and is used to indicate that
a destination device corresponding to the first target address
stops receiving a unicast packet with the multicast identifier. The
determining unit is further configured to search for the first
multicast routing entry corresponding to the multicast identifier,
and determine that the first target address belongs to the
destination address group. The processing unit is further
configured to remove the first target address from the first
multicast routing entry, and stop sending the unicast packet with
the multicast identifier to the destination device corresponding to
the first target address.
In one embodiment, the sending unit is further configured to: when
the determining unit determines that a destination address in the
first multicast routing entry from which the first target address
is removed is empty, instruct the upstream multicast router to stop
sending the unicast packet with the multicast identifier to the
sending unit.
According to a fourth aspect, an embodiment of this application
further provides a multicast forwarding apparatus, and the
apparatus has functions of implementing behavior of a terminal in
the method example of the foregoing second aspect. The functions
may be implemented by hardware, or may be implemented by hardware
by executing corresponding software. The hardware or the software
includes one or more modules corresponding to the functions. The
apparatus includes a receiving unit, a processing unit, and a
second multicast router of a method side corresponding to the
apparatus. The receiving unit is configured to receive a prune
message from a downstream multicast router, where the prune message
includes a destination address group determined by the downstream
multicast router from all unicast packets in a unicast packet set,
the unicast packet set is a set of unicast packets that are
obtained by the downstream multicast router by listening to a
plurality of unicast packets passing through the downstream
multicast router, that are from the second multicast router, and
that belong to a same unicast stream, a unicast packet in the
unicast stream carries a multicast identifier, and the multicast
identifier indicates that the unicast packets in the unicast stream
are from a same data source server and are to be sent to
destination devices that belong to a same multicast group. The
processing unit is configured to stop, based on the prune message,
sending the unicast packets with the multicast identifier to the
destination devices corresponding to the destination address group.
The sending unit is configured to send the to-be-sent unicast
packets with the multicast identifier to the downstream multicast
router.
In one embodiment, the receiving unit is further configured to
receive a registration request from the data source server, where
the registration request carries IP four-tuple information of a
User Datagram Protocol (UDP) session. The processing unit is
further configured to allocate a multicast group identifier to the
UDP session based on the registration request. The sending unit is
further configured to send a registration request response message
to the data source server, where the response message carries the
multicast group identifier. The receiving unit is further
configured to receive a unicast packet sent by the data source
server, where a header of the unicast packet carries the multicast
identifier, and the multicast identifier is generated by the data
source server based on an address of the data source server and the
multicast group identifier.
In one embodiment, the receiving unit is configured to receive an
on-demand request from a first client, where the on-demand request
is used to request to subscribe to the UDP session. The forwarding
apparatus further includes a generation unit. The generation unit
is configured to generate a second multicast routing entry, where a
source address of the second multicast routing entry is an address
of the second multicast router, and a destination address of the
second multicast routing entry is an address of the first
client.
In one embodiment, the forwarding apparatus further includes the
processing unit, configured to modify the received unicast packet
with the multicast identifier based on the second multicast routing
entry, to obtain a modified unicast packet, where a source address
of the modified unicast packet is the address of the second
multicast router, and a destination address of the modified unicast
packet is the address of the first client. The sending unit is
configured to send the modified unicast packet with the multicast
identifier to the first client.
In one embodiment, the receiving unit is configured to receive an
on-demand stop request sent by the first client, where the
on-demand stop request is used to request to stop subscribing to
the UDP session. The processing unit is further configured to:
search for the second multicast routing entry corresponding to the
multicast identifier; determine that the address of the first
client is included in the destination address of the second
multicast routing entry; remove the address of the first client
from the second multicast routing entry; and stop sending the
unicast packet with the multicast identifier to a destination
device corresponding to the address of the first client.
In one embodiment, the processing unit is further configured to
search for the second multicast routing entry corresponding to the
multicast identifier; determine that the address of the first
client is not included in the destination address of the second
multicast routing entry; and generate a first message based on the
second multicast routing entry, where a source address of the first
message is the address of the second multicast router, a
destination address of the first message is the address of the
first client, and the first message carries the multicast
identifier, and is used to notify the downstream multicast router
that a destination device corresponding to the first target address
stops receiving a unicast packet with the multicast identifier. The
sending unit is configured to send the first message to the first
client, so that the downstream multicast router stops, after
obtaining the first message through listening, sending the unicast
packet with the multicast identifier to the first client.
According to a fifth aspect, an embodiment of this application
further provides a multicast router, and the multicast router has
functions of implementing behavior of a multicast router in the
method example of the first aspect or the second aspect. The
functions may be implemented by hardware. A structure of the
terminal includes a communications interface, a processor, and a
memory, and the processor invokes an instruction stored in the
memory, to perform the foregoing method.
According to a sixth aspect, an embodiment of this application
further provides a computer storage medium, and the storage medium
stores a software program. When being read and executed by one or
more processors, the software program may implement the method
provided in the first aspect or any embodiments of the first
aspect.
According to a seventh aspect, this application further provides a
computer program product that includes an instruction. When the
computer program product runs on a computer, the computer is
enabled to perform the foregoing aspects or various
embodiments.
Compared with conventional IP multicast, in the multicast
forwarding method provided in the embodiments of this application,
a packet whose unicast address is a destination address may pass
through a unicast network, and carries a multicast identifier, so
that the multicast router may identify the packet. Therefore, the
multicast function can be implemented in the network when some
devices support multicast. In addition, some same unicast streams
may be combined when the multicast function is implemented, thereby
reducing network bandwidth consumption.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is an architectural diagram of a communications system
according to an embodiment of this application;
FIG. 2A, FIG. 2B, and FIG. 2C are an interaction diagram of
Scenario 1 of a multicast forwarding method according to an
embodiment of this application;
FIG. 3A and FIG. 3B are an interaction diagram of Scenario 2 of a
multicast forwarding method according to an embodiment of this
application;
FIG. 4A and FIG. 4B are an interaction diagram of Scenario 3 of a
multicast forwarding method according to an embodiment of this
application;
FIG. 5 is a diagram of an example architecture of a multicast
forwarding method according to an embodiment of this application;
and
FIG. 6 is a schematic structural diagram of a multicast router
according to an embodiment of this application.
DESCRIPTION OF EMBODIMENTS
The following further describes this application in detail with
reference to the accompanying drawings.
A multicast forwarding method in this application is applicable to
various communications systems. FIG. 1 is a schematic diagram of
one of the communications systems to which this application is
applicable. The communications system includes a data source
server, a rendezvous point (RP), a multicast router (MCR) 1, an MCR
2, an R1 to an R8, and a terminal 1 to a terminal 5.
The RP, the MCR 1, and the MCR 2 are introduced multicast routers
that support multicast in an embodiment of this application. The R1
to the R8 are common routers, and do not support a multicast
function. The terminal 1 to the terminal 5 may be computer devices,
various mobile terminal devices, or the like. It should be noted
that the RP is a special multicast router, and is further
responsible for allocating a multicast group identifier,
interacting with a client, and the like in addition to having the
multicast function. In addition, the MCR 1 and the MCR 2 are
multicast routers that support the multicast function, and are
responsible for listening to and identifying unicast streams that
can be aggregated, and aggregating these unicast streams.
Considering an existing IP multicast disadvantage that all routers
in a network need to support the PIM-SM protocol and unicast
disadvantages of a network bandwidth waste and low transmission
efficiency, functions of some routers are upgraded based on an
existing unicast network architecture in this embodiment of this
application, so that the upgraded routers have the multicast
function. The multicast function indicates that a multicast source
sends information only once, a multicast router establishes a
tree-like route by using a multicast routing protocol, and the
transmitted information starts to be copied and distributed at a
branch away from the multicast source as far as possible. In a
multicast manner, a sender of information is referred to as a
"multicast source", a receiver of information is referred to as a
"multicast group" of the information, and all routers supporting
multicast information transmission are referred to as "multicast
routers". Receivers joining a same multicast group may be widely
distributed in any location in the network. In other words, the
"multicast group" is not geographically limited. It should be noted
that a plurality of multicast sources may simultaneously send
information to a same multicast group. It is assumed that only a
terminal B, a terminal D, and a terminal E need same information.
When the multicast manner is used, these terminals may join a same
multicast group. The multicast source needs to send only one piece
of information to an upstream multicast router, and each downstream
multicast router in the network copies and forwards the information
based on distribution of all the members in the multicast group.
Finally, the information is accurately distributed to the terminal
B, the terminal D, and the terminal E.
It can be learned from FIG. 1 that the communications system
provided in this embodiment of this application improves only the
router RP, the router MCR 1, and the router MCR 2. The improved RP,
MCR 1, and MCR 2 have the multicast function. None of the common
routers R1 to R8 participates in a multicast signaling process.
Therefore, compared with IP multicast, the communications system
provided in this embodiment of this application does not need to
deploy multicast routers on the entire network. The RP, the MCR 1,
and the MCR 2 having the multicast function do not use addresses of
multicast groups in which the terminals are located as destination
addresses. Instead, the RP, the MCR 1, and the MCR 2 having the
multicast function mark a multicast packet by using a multicast
identifier formed by an address of the data source server and a
multicast group identifier.
Because the data source server inserts a multicast identifier into
a packet, a multicast router on a branch tree generates a unicast
packet set by listening to a unicast packet passing through the
multicast router, and each unicast packet set includes unicast
packets that are from a same multicast source and that carry a same
multicast identifier. Once the multicast router MCR 2 on the branch
tree detects that destination addresses (namely, the terminal 3 and
the terminal 4) of unicast packets in the unicast packet set are
different, a plurality of same unicast streams corresponding to
different destination addresses are combined. In other words, the
upstream multicast router MCR 2 is instructed to no longer send the
plurality of same unicast streams but send only one unicast stream
to the multicast router MCR 1, and the multicast router MCR 2
distributes the unicast stream to destination devices (namely, the
terminal 3 and the terminal 4) corresponding to the different
destination addresses. In this way, a packet whose unicast address
is a destination address may pass through a unicast network, and
the multicast identifier needs to be identified only by the
multicast router, so that the multicast function can be implemented
in the network when some devices support multicast. In addition,
some same unicast streams may be combined when the multicast
function is implemented, thereby reducing network bandwidth
consumption.
In this embodiment of this application, a process of the multicast
forwarding method is further described in detail with reference to
the communications system shown in FIG. 1. There is an enabling
sequence of multicast routers in the communications system shown in
FIG. 1. In other words, the multicast routers may have the
multicast function at different times. Therefore, the embodiments
of this application are separately described in the following three
scenarios.
Scenario 1
As shown in FIG. 2A, FIG. 2B, and FIG. 2C, a main procedure
includes: a registration procedure A, an on-demand procedure B, a
combination procedure C, and an on-demand stop procedure D.
The registration procedure A mainly includes operation 201 to
operation 203 in FIG. 2A. Content is as follows:
Operation 201: A data source server sends a registration request to
a multicast router, where IP four-tuple (a source address, a
destination address, a source port number, and a destination port
number) information of a UDP session is carried during
registration.
Operation 202: After receiving the registration request of the data
source server, the RP allocates a multicast group identifier to the
UDP session based on the IP four-tuple of the UDP session in the
registration request, and records a mapping relationship between
the IP four-tuple of the UDP session and the multicast group
identifier. In addition, the RP sends a registration request
response message to the data source server, and the response
message carries the multicast group identifier.
Operation 203: After receiving the response message of the
multicast router, the data source server forms a multicast
identifier by using the multicast group identifier allocated by the
RP and an address of the data source server, inserts the multicast
identifier into a header of a unicast packet, and then sends a
modified packet to the RP. For example, if the address of the data
source server is 10.0.0.2, and the multicast group identifier
allocated by the RP to the UDP session is 1, the multicast
identifier generated by the data source server is
(10.0.0.2::1).
The on-demand procedure B mainly includes operation 204a to
operation 205e in FIG. 2A. Content is as follows:
Operation 204a to operation 204e: A terminal 1 to a terminal 5 send
on-demand requests to the RP, where the on-demand requests carry a
group identifier of a multicast group in which the terminal 1 to
the terminal 5 are located.
Operation 205a to operation 205e: After receiving the on-demand
requests of the terminals, the RP queries, based on the multicast
group identifiers of the terminals in the on-demand requests, the
pre-established mapping relationship between the IP four-tuple of
the UDP session and the multicast group identifier, and determines
the corresponding UDP session. For example, the RP receives the
on-demand request of the terminal 1, a multicast group identifier
of the terminal in the on-demand request is 1, and the RP
determines that the data source server of the UDP session is
10.0.0.2. Further, the RP adds an address of the terminal 1 to a
multicast routing entry 1 (for example, as shown in Table 1). A
source address in the multicast routing entry 1 is an address of
the RP, and a destination address is the address of the terminal 1.
The RP modifies, based on the multicast routing entry 1, a packet
in the UDP session into a unicast packet whose source address is
the RP and whose destination address is the address of the terminal
1, sends the unicast packet, and adds the multicast identifier to
the unicast packet.
TABLE-US-00001 TABLE 1 Multicast identifier Source address
Destination address (10.0.0.2::1) Address of the RP Address of the
terminal 1 Address of the terminal 2 Address of the terminal 3
Address of the terminal 4 Address of the terminal 5
The combination procedure C is mainly as follows: In FIG. 2B, the
MCR 1 aggregates unicast streams sent by the RP to the terminal 2
to the terminal 5 (refer to operation 206 to operation 209e), and
the MCR 2 aggregates unicast streams sent by the MCR 1 to the
terminal 3 and the terminal 4 (refer to operation 210 to operation
213d). Content is as follows.
Operation 206: An MCR 1 and an MCR 2 listen to unicast packets
passing through the MCR 1 and the MCR 2, and obtain multicast
identifiers of the unicast packets obtained through listening and
source address information in the unicast packets.
Operation 207a: The MCR 1 determines that there are n unicast
packets whose source addresses are an address of the RP and that
all the n unicast packets have a same multicast identifier
(10.0.0.2::1); combines then unicast packets into one unicast
packet set; and determines addresses of four terminals (the
terminal 2 to the terminal 5) in the unicast packet set. Therefore,
the MCR 1 sends a prune message to the upstream RP, where the prune
message carries a destination address group (including the
addresses of the terminal 2 to the terminal 5) determined from all
the unicast packets in the unicast packet set. In addition, the MCR
1 generates a multicast routing entry 2 (for example, as shown in
Table 2). A source address in the multicast routing entry 2 is an
address of the MCR 1, and a destination address is the addresses of
the terminal 2 to the terminal 5.
TABLE-US-00002 TABLE 2 Multicast identifier Source address
Destination address (10.0.0.2::1) Address of the MCR 1 Address of
the terminal 2 Address of the terminal 3 Address of the terminal 4
Address of the terminal 5
Operation 207b: The MCR 2 also determines that there are k unicast
packets whose source addresses are the address of the RP and that
all the k unicast packets have the same multicast identifier
(10.0.0.2::1); combines the k unicast packets into one unicast
packet set; and determines addresses of two terminals (the terminal
3 and the terminal 4) in the unicast packet set. Therefore, the MCR
2 sends a prune message to the upstream RP. It should be noted
that, because the communications system in FIG. 1 has a tree-like
structure of a branch tree, in a time sequence, the MCR 1 obtains a
unicast packet through listening before the MCR 2, and therefore
the MCR 1 sends the prune message to the RP before the MCR 2.
Therefore, the RP first receives the prune message sent by the MCR
1.
Operation 208: Because the prune message is used to instruct the RP
to stop sending unicast packets with the multicast identifier to
destination devices (the terminal 2 to the terminal 5)
corresponding to the destination address group, and send the
to-be-sent unicast packets with the multicast identifier to the MCR
1, after receiving the prune message sent by the MCR 1, the RP
finds the corresponding multicast routing table 1 by using the
multicast identifier, modifies the multicast routing entry 1,
replaces the addresses of the terminal 2 to the terminal 5 with the
address of the MCR 1, then combines a plurality of unicast streams
to be sent to the terminal 2 to the terminal 5 into one unicast
stream, and sends the unicast stream to the MCR 1. Table 3 shows a
multicast routing entry 1 obtained after modification.
TABLE-US-00003 TABLE 3 Multicast identifier Source address
Destination address (0.0.0.2::1) Address of the RP Address of the
terminal 1 Address of the MCR 1
Then, because the RP also receives the prune message of the MCR 2,
and the multicast routing entry 1 (refer to Table 3) of the RP no
longer includes the destination addresses of the terminal 3 and the
terminal 4, the RP does not respond to the prune message.
Operation 209b to operation 209e: After receiving a unicast packet
of the combined unicast stream sent by the RP, the MCR 1 copies and
distributes the received unicast packet of the unicast stream to
the terminal 2 to the terminal 5 based on the multicast routing
entry 2 in Table 2.
Operation 210: The MCR 2 listens to a unicast packet passing
through the MCR 2, and obtains a multicast identifier of the
unicast packet obtained through listening and source address
information in the unicast packet.
Operation 211: The MCR 2 determines that there are m unicast
packets whose source addresses are the address of the MCR 1 and
that all the m unicast packets have the same multicast identifier
(10.0.0.2::1); combines the m unicast packets into one unicast
packet set; and determines addresses of two terminals (the terminal
3 and the terminal 4) in the unicast packet set. Therefore, the MCR
2 sends a prune message to the upstream MCR 1, where the prune
message carries a destination address group (including the
addresses of the terminal 3 and the terminal 4) determined from all
the unicast packets in the unicast packet set. In addition, the MCR
2 generates a multicast routing entry 3 (for example, as shown in
Table 4). A source address in the multicast routing entry 3 is an
address of the MCR 2, and a destination address is the addresses of
the terminal 3 and the terminal 4.
TABLE-US-00004 TABLE 4 Multicast identifier Source address
Destination address (10.0.0.2::1) Address of the MCR 2 Address of
the terminal 3 Address of the terminal 4
Operation 212: Because the prune message is used to instruct the
MCR 1 to stop sending unicast packets with the multicast identifier
to destination devices (the terminal 3 and the terminal 4)
corresponding to the destination address group, and send the
to-be-sent unicast packets with the multicast identifier to the MCR
2, after receiving the prune message, the MCR 1 finds the
corresponding multicast routing table 2 by using the multicast
identifier, modifies the multicast routing entry 2, replaces the
addresses of the terminal 3 and the terminal 4 with the address of
the MCR 2, then combines a plurality of unicast streams to be sent
to the terminal 3 and the terminal 4 into one unicast stream, and
sends the unicast stream to the MCR 2. Table 5 shows a multicast
routing entry 2 obtained after modification.
TABLE-US-00005 TABLE 5 Multicast identifier Source address
Destination address (10.0.0.2::1) Address of the MCR 1 Address of
the terminal 2 Address of the MCR 2 Address of the terminal 5
Operation 213c to operation 213d: After receiving a unicast packet
of the combined unicast stream sent by the MCR 1, the MCR 2 copies
and distributes the received unicast packet of the unicast stream
to the terminal 3 and the terminal 4 based on the multicast routing
entry 3 in Table 4.
The on-demand stop procedure D mainly includes operation 214 to
operation 216 in FIG. 2C. Content is as follows:
Operation 214: The terminal sends an on-demand stop request to the
RP, where the on-demand stop request carries the multicast
identifier and a first target address, and is used to indicate that
a destination device corresponding to the first target address
stops receiving a unicast packet with the multicast identifier. For
example, the terminal 2 sends the on-demand stop request to the RP,
and the on-demand stop request carries an address of the terminal 2
and the multicast identifier (10.0.0.2::1).
Operation 215: The RP searches for the multicast routing entry 1
corresponding to the multicast identifier, determines that the
address of the terminal 2 is not included in a destination address
list of the multicast routing entry 1, and notifies, by using a
first message, the downstream multicast router that the terminal 2
stops receiving a unicast packet with the multicast identifier,
where a source address of the first message is the address of the
RP, and a destination address is addresses of the terminal 1 to the
terminal 5.
Operation 216: The MCR 1 obtains the first message during
listening, finds a corresponding multicast identifier based on the
multicast identifier in the first message, then determines the
multicast routing entry 2 through searching based on the multicast
identifier, modifies the multicast routing entry 2, and removes the
address of the terminal 2 from the multicast routing entry 2. Table
6 shows a multicast routing entry 2 obtained after
modification.
TABLE-US-00006 TABLE 6 Multicast identifier Source address
Destination address (10.0.0.2::1) Address of the MCR 1 Address of
the MCR 2 Address of the terminal 5
Assuming that the terminal 1 sends the on-demand stop request to
the RP in operation 214, operation 215 and operation 216 are as
follows: The RP searches for the multicast routing entry 1
corresponding to the multicast identifier, determines that the
address of the terminal 2 is included in the destination address
list of the multicast routing entry 1, modifies the multicast
routing entry 1, and removes the address of the terminal 1 from the
multicast routing entry 1. Table 7 shows a multicast routing entry
1 obtained after modification.
TABLE-US-00007 TABLE 7 Multicast identifier Source address
Destination address (10.0.0.2::1) Address of the RP Address of the
MCR 1
It can be learned from the procedures described in FIG. 2A, FIG.
2B, and FIG. 2C that, in this embodiment of this application, a
multicast transmission service function is implemented by deploying
some multicast routes in a unicast network, so that some multicast
functions can be implemented, network bandwidth occupation can be
reduced, and the multicast router may further count added or
removed terminals by using a multicast routing entry, to manage and
charge the terminal.
It should be noted that, assuming that the prune message sent by
the MCR 1 in operation 207a is lost and subsequently resent,
subsequent execution operations are different. Details are as
follows:
Operation 208: Because the prune message is used to instruct the RP
to stop sending unicast packets with the multicast identifier to
destination devices (the terminal 3 and the terminal 4)
corresponding to the destination address group, and send the
to-be-sent unicast packets with the multicast identifier to the MCR
2, after receiving the prune message sent by the MCR 2, the RP
finds the corresponding multicast routing table 1 by using the
multicast identifier, modifies the multicast routing entry 1,
replaces the addresses of the terminal 3 and the terminal 4 with
the address of the MCR 2, then combines a plurality of unicast
streams to be sent to the terminal 3 and the terminal 4 into one
unicast stream, and sends the unicast stream to the MCR 2.
Then, because the RP also receives the prune message of the MCR 1,
and the multicast routing entry 1 of the RP no longer includes the
destination addresses of the terminal 3 and the terminal 4, the RP
does not combine the two unicast streams. Instead, the RP only
combines the addresses sent to the terminal 2, the terminal 5, and
the MCR 1 into one unicast stream, and then sends the unicast
stream to the MCR 1. After the MCR combines the unicast streams of
the RP and before the MCR 1 completes combination, the MCR 2
follows the following principle: combining only packets whose
source addresses are the upstream MCR 1.
Scenario 2
It is assumed that the MCR 2 is a common router at an initial
deployment stage of the communications system in FIG. 1, and is
subsequently upgraded to a multicast router due to a product
requirement. In the combination procedure 303, operations performed
when the MCR 2 in FIG. 1 is a common router are different from
those performed when the MCR 2 is upgraded to a multicast
router.
Case 1: As shown in FIG. 3A and FIG. 3B, when the MCR 2 is a common
router, a packet forwarding process includes the following
operations:
Operation 301 to operation 305e are consistent with operation 201
to operation 205e, and details are not described herein again.
Operation 306: The MCR 1 listens to a unicast packet passing
through the MCR 1, and obtains a multicast identifier of the
unicast packet obtained through listening and source address
information in the unicast packet.
Operation 307a is consistent with operation 207a, and details are
not described herein again.
Operation 308: Because the prune message is used to instruct the RP
to stop sending unicast packets with the multicast identifier to
destination devices (the terminal 2 to the terminal 5)
corresponding to the destination address group, and send the
to-be-sent unicast packets with the multicast identifier to the MCR
1, after receiving the prune message sent by the MCR 1, the RP
finds the corresponding multicast routing entry 1 by using the
multicast identifier, modifies the multicast routing entry 1,
replaces the addresses of the terminal 2 to the terminal 5 with the
address of the MCR 1, then combines a plurality of unicast streams
to be sent to the terminal 2 to the terminal 5 into one unicast
stream, and sends the unicast stream to the MCR 1. Table 3 shows
the multicast routing entry 1 obtained after modification.
Operation 309b to operation 309e are consistent with operation 209b
to operation 209e, and details are not described herein again.
Case 2: When the MCR 2 is upgraded to a multicast router,
operations in a packet forwarding process are the same as
operations in FIG. 2A, FIG. 2B, and FIG. 2C. A difference lies in
that the MCR 2 and the MCR 1 do not simultaneously send a prune
message to the RP. In other words, because the MCR 1 has combined
unicast streams sent by the RP, there is no operation 307b. As
shown in FIG. 3A and FIG. 3B, the MCR 2 performs the following
operations:
Operation 310: The MCR 2 listens to a unicast packet passing
through the MCR 2, and obtains a multicast identifier of the
unicast packet obtained through listening and source address
information in the unicast packet.
Operation 311 to operation 313d are consistent with operation 211
to operation 211d, and details are not described herein again.
Scenario 3
It is assumed that the MCR 1 is a common router at an initial
deployment stage of the communications system in FIG. 1, and is
subsequently upgraded to a multicast router due to a product
requirement. In the combination procedure 303, operations performed
when the MCR 1 in FIG. 1 is a common router are different from
those performed when the MCR 1 is upgraded to a multicast
router.
Case 1: As shown in FIG. 4A and FIG. 4B, when the MCR 1 is a common
router, a packet forwarding process includes the following
operations:
Operation 401 to operation 405e are consistent with operation 201
to operation 205e, and details are not described herein again.
Operation 406 is consistent with operation 210, and details are not
described herein again.
Operation 407: The MCR 2 determines that there are m unicast
packets whose source addresses are an address of the RP and that
all the m unicast packets have a same multicast identifier
(10.0.0.2::1); combines the m unicast packets into one unicast
packet set; and determines addresses of two terminals (the terminal
3 and the terminal 4) in the unicast packet set. Therefore, the MCR
2 sends a prune message to the upstream RP, where the prune message
carries a destination address group (including the addresses of the
terminal 3 and the terminal 4) determined from all the unicast
packets in the unicast packet set. In addition, the MCR 2 generates
a multicast routing entry 3 (as shown in Table 4).
Operation 408: Because the prune message is used to instruct the RP
to stop sending unicast packets with the multicast identifier to
destination devices (the terminal 3 and the terminal 4)
corresponding to the destination address group, and send the
to-be-sent unicast packets with the multicast identifier to the MCR
2, after receiving the prune message, the RP finds the
corresponding multicast routing table 2 by using the multicast
identifier, modifies the multicast routing entry 1, replaces the
addresses of the terminal 3 and the terminal 4 with the address of
the MCR 2, then combines a plurality of unicast streams to be sent
to the terminal 3 and the terminal 4 into one unicast stream, and
sends the unicast stream to the MCR 2. Table 8 shows a multicast
routing entry 1 obtained after modification.
TABLE-US-00008 TABLE 8 Multicast identifier Source address
Destination address (10.0.0.2::1) Address of the RP Address of the
terminal 1 Address of the terminal 2 Address of the MCR 2 Address
of the terminal 5
Case 2: When the MCR 1 is upgraded to a multicast router,
operations in a packet forwarding process are the same as
operations in FIG. 2A, FIG. 2B, and FIG. 2C. In addition to that
the MCR 1 and the MCR 2 do not simultaneously send a prune message
to the RP, a difference further lies in that, because the MCR 2 has
combined unicast streams of the terminal 3 and the terminal 4, the
MCR 1 sends a prune message to the RP only to request to combine
unicast streams to be sent to the terminal 2, the terminal 5, and
the MCR 1. As shown in FIG. 4A and FIG. 4B, operations are as
follows.
Operation 410: The MCR 1 listens to a unicast packet passing
through the MCR 1, and obtains a multicast identifier of the
unicast packet obtained through listening and source address
information in the unicast packet.
Operation 411: The MCR 1 determines that there are L unicast
packets whose source addresses are an address of the RP and that
all the L unicast packets have a same multicast identifier
(10.0.0.2::1); combines the L unicast packets into one unicast
packet set; and determines addresses of three terminals (the
terminal 2, the MCR 2, and the terminal 5) from the unicast packet
set. Therefore, the MCR 1 sends a prune message to the RP, where
the prune message carries a destination address group (including
the address of the terminal 2, the address of the MCR 2, and the
address of the terminal 5) determined from all the unicast packets
in the unicast packet set. In addition, the MCR 1 generates a
multicast routing entry 2 (as shown in Table 9). A source address
in the multicast routing entry 2 is an address of the MCR 1, and a
destination address is the addresses of the terminal 2, the MCR 2,
and the terminal 5.
TABLE-US-00009 TABLE 9 Multicast identifier Source address
Destination address (10.0.0.2::1) Address of the Address of the
terminal 2 MCR 1 Address of the MCR 2 Address of the terminal 5
Operation 412b, operation 402e, and operation 402f: After receiving
a unicast packet of the combined unicast stream sent by the RP, the
MCR 1 copies and distributes the received unicast packet of the
unicast stream to the terminal 3, the MCR 2, and the terminal 5
based on the multicast routing entry 2 in Table 9.
To describe the foregoing multicast forwarding method more vividly,
in this embodiment of this application, the foregoing packet
forwarding process is described with reference to a communications
system of a relatively simple network architecture shown in FIG. 5,
and the communications system in FIG. 5 includes a data source
server, an RP, an MCR 1, an R1 to an R4, and a terminal 1 to a
terminal 3 joining a same multicast group.
Table 10 shows addresses of network elements in FIG. 5.
TABLE-US-00010 TABLE 10 Data source server 10.0.0.2 RP 10.0.0.1 MCR
1 10.10.0.1 R1 10.9.0.1 R2 10.9.10.1 R3 10.10.9.1 R4 10.10.10.1
Terminal 1 10.9.10.2 Terminal 2 10.10.9.2 Terminal 3 10.10.10.2
A first procedure in FIG. 5: The data source server initiates a
registration procedure to the RP, and detailed operations are as
follows:
(A1) The data source server initiates establishment of a UDP
session to the RP, where a source address of the UDP session is
10.0.0.2, a destination address is 10.0.0.1, a source port number
is 112, and a destination port number is 211.
(A2) The data source server sends a registration request to the RP,
where the registration request carries IP four-tuple information of
the UDP session.
(A3) After receiving the registration request, the RP searches, by
using the IP four-tuple information, a table of a pre-established
mapping relationship between an IP four-tuple and a multicast group
identifier. If no result is found and multicast group identifier
resources are sufficient, the RP allocates a multicast group
identifier ID 1 to the UDP session.
(A4) The RP generates a mapping relationship between the IP
four-tuple and the multicast group identifier ID 1.
(A5) The RP sends a response message to the data source server, and
generates a multicast identifier (10.0.0.2::1).
(A6) The RP establishes a multicast routing entry 1 corresponding
to the multicast identifier (10.0.0.2::1), where a source address
is an address (10.0.0.1) of the RP, and a destination address list
is empty.
(A7) The data source server sends multicast content to the RP by
using the UDP session, and inserts the multicast identifier
(10.0.0.2::1) into a packet header.
A second procedure: The terminal 1 initiates an on-demand procedure
to the RP. Detailed operations are as follows:
(B1) The RP receives an on-demand request sent by the terminal 1,
and determines the IP four-tuple of the UDP session between the RP
and the data source server based on multicast group identifier
information in the on-demand request.
(B2) The RP obtains the multicast identifier (10.0.0.2::1) by using
the IP four-tuple, finds the multicast routing entry 1
corresponding to the multicast identifier, and adds an address
(10.9.10.2) of the terminal 1 to the destination list of the
entry.
(B3) The RP records, in a context of the terminal 1, that a sending
status of the terminal 1 is "direct sending", and copies one
unicast stream to the terminal 1.
A third procedure: The terminal 2 initiates an on-demand procedure
to the RP. Detailed operations are as follows:
(C1) The RP receives an on-demand request sent by the terminal 2,
and determines the IP four-tuple of the UDP session between the RP
and the data source server based on multicast group identifier
information in the on-demand request.
(C2) The RP obtains the multicast identifier (10.0.0.2::1) by using
the IP four-tuple, finds the multicast routing entry 1
corresponding to the multicast identifier, and adds an address
(10.10.9.2) of the terminal 2 to the destination list of the
entry.
(C3) The RP records, in a context of the terminal 2, that a sending
status of the terminal 2 is "direct sending", and copies one
unicast stream to the terminal 2.
A fourth procedure: The terminal 3 initiates an on-demand procedure
to the RP. Detailed operations are as follows:
(D1) The RP receives a request sent by the terminal 3, and
determines the IP four-tuple of the UDP session between the RP and
the data source server based on multicast group identifier
information in the on-demand request.
(D2) The RP obtains the multicast identifier (10.0.0.2::1) by using
the IP four-tuple, finds the multicast routing entry 1
corresponding to the multicast identifier, and adds an address
(10.10.10.2) of the terminal 3 to the destination list of the
entry.
(D3) The RP records, in a context of the terminal 3, that a sending
status of the terminal 3 is "direct sending", and copies one
unicast stream to the terminal 3.
A fifth procedure: Combination procedure. Detailed operations are
as follows:
(E1) The MCR 1 obtains, through listening by using a matching rule
1, a packet whose destination address is the address (10.10.9.2) of
the terminal 2 and whose source address is the address (10.0.0.1)
of the RP and that has the multicast identifier (10.0.0.2::1), and
also obtains, through listening, a packet whose destination address
is the address (10.10.10.2) of the terminal 3 and whose source
address is the address (10.0.0.1) of the RP and that has the
multicast identifier (10.0.0.2::1). The rule 1 means that packets
that are sent by a same upstream multicast router and that have a
same multicast identifier are obtained through matching, to obtain
a unicast packet set.
(E2) Because more than one address in the destination list is
copied, the MCR 1 sends a prune message to the RP, to instruct the
RP to combine two unicast streams that have the same multicast
identifier and that are sent to the terminal 2 and the terminal 3.
A destination address of the prune message is the address
(10.0.0.1) of the RP, a source address is the address (10.10.0.1)
of the MCR 1, and the prune message carries a destination address
list (10.10.9.2 and 10.10.10.2) and the multicast identifier
(10.0.0.2::1).
(E3) The RP receives the prune message, finds the corresponding
multicast routing entry 1 by using the multicast identifier
(10.0.0.2::1), deletes (10.10.9.2) and (10.10.10.2) from the
destination address list, adds the address (10.10.0.1) of the MCR 1
to the destination address list, and denotes sending modes of the
terminal 2 and the terminal 3 as indirect sending.
(E4) The MCR 1 generates a multicast routing entry 2 corresponding
to the multicast identifier (10.0.0.2::1), where a source address
is the address (10.0.0.1) of the MCR 1, and the destination address
list includes addresses of the terminal 2 and the terminal 3.
(E5) A rule 2 is added by the MCR and is delivered before the rule
1. A priority of the rule 2 is higher than a priority of the rule
1. Content of the rule 1 is mainly as follows: When a unicast
packet that has the multicast identifier (10.0.0.2::1) and whose
source address is the RP and whose destination address is the MCR
is obtained through matching, the unicast packet is not added to
the unicast packet set. It is designed to prevent a combined
unicast stream from being matched again by using the rule 1.
A sixth procedure: On-demand stop procedure. Detailed operations
are as follows:
(F1) The RP receives an on-demand stop request sent by the terminal
3, learns that a sending status of the terminal 3 is indirect
sending, and constructs a stop-copy message, where a destination
address of the stop-copy message is the address (10.10.10.2) of the
terminal 3, and the stop-copy message carries the multicast
identifier (10.0.0.2::1).
(F2) The MCR 1 obtains the stop-copy message through listening by
using a rule 3, searches for the multicast routing entry 2 by using
a multicast group ID in the message, checks a destination address
of the terminal 3 in the destination list of the entry, deletes the
destination address, and sends a response to the RP. Content of the
rule 3 is used to match the stop-copy message of the RP.
It can be learned from the foregoing example that, the MCR 1
instructs the RP to combine a plurality of unicast streams, and the
MCR 1 sends a combined unicast stream to each destination device,
thereby effectively reducing network bandwidth.
FIG. 6 is a schematic structural diagram of a multicast router
according to this application. The multicast router 800 includes a
communications interface 801, a processor 802, a memory 803, and a
bus system 804. The multicast router may be a first multicast
router, or may be a second multicast router.
The memory 803 is configured to store a computer program, and may
further store some data information and the like received by the
multicast router. In one embodiment, the computer program may
include program code, and the program code may include a computer
operation instruction and the like. The memory 803 may be a random
access memory (RAM), or may be a nonvolatile memory (NVM), for
example, at least one magnetic disk storage. Only one memory is
shown in the figure. Certainly, a plurality of memories may be
provided as required. Alternatively, the memory 803 may be a memory
in the processor 802.
For example, the memory 803 may store the following elements,
executable modules, data structures, or the like, or a subset
thereof, or an extension set thereof:
an operation instruction: including various operation instructions,
and used to implement various operations; and
an operating system, including various system programs, and used to
implement various basic services and process a hardware-based
task.
The processor 802 is configured to control an operation of the
multicast router 800, and the processor 802 may be further referred
to as a central processing unit (CPU).
The communications interface 801 is configured to perform
processing such as information receiving and sending with another
device connected to the multicast router 800.
In application, components of the multicast router 800 may be
coupled together by using the bus system 804. In addition to a data
bus, the bus system 804 may further include a power bus, a control
bus, a status signal bus, and the like. However, for clarity of
description, various buses are marked as the bus system 804 in the
figure. For ease of illustration, FIG. 6 merely shows an example of
the multicast router 800.
The method disclosed in the embodiments of this application may be
applied to the processor 802, or may be implemented by the
processor 802. The processor 802 may be an integrated circuit chip
and has a signal processing capability. In an implementation
process, each operation of the foregoing method may be completed by
using an integrated logic circuit of hardware in the processor 802
or an instruction in a form of software. The processor 802 may be a
general purpose processor, a digital signal processor (DSP), an
application-specific integrated circuit (ASIC), a field
programmable gate array (FPGA) or another programmable logic
device, a discrete gate or transistor logic device, or a discrete
hardware component. All methods, operations, and logical block
diagrams disclosed in the embodiments of this application may be
implemented or performed. The general purpose processor may be a
microprocessor or the processor may be any conventional processor,
or the like. Operations of the methods disclosed in the embodiments
of this application may be directly performed and completed by a
hardware decoding processor, or may be performed and completed by
using a combination of hardware in the decoding processor and a
software module. The software module may be located in a mature
storage medium in the field, such as a random access memory, a
flash memory, a read-only memory, a programmable read-only memory,
an electrically-erasable programmable memory, or a register. The
storage medium may be located in the memory 803, and the processor
802 may read information stored in the memory 803, and perform the
foregoing method operations with reference to hardware.
When the multicast router in the foregoing embodiment is the first
multicast router, the multicast router may send a prune message to
an upstream router, and copy and distribute a combined unicast
stream sent by the upstream router to a destination device. If the
multicast router is the second multicast router, namely, an RP, the
multicast router may communicate with a data source server, and
allocate a multicast identifier to a UDP session. In addition,
after receiving a prune message, the multicast router may combine a
plurality of unicast streams, and send a combined unicast stream to
the downstream multicast router. For implementation, refer to
descriptions in the foregoing method embodiment, and details are
not described herein again.
In conclusion, a unicast packet in this embodiment of this
application is copied and distributed by using a multicast router
deployed in a unicast network. This can reduce network bandwidth
and server overheads compared with unicast transmission. In
addition, in this embodiment of this application, multicast routers
do not need to be deployed in an entire network, and only a limited
quantity of existing routers need to be upgraded. In addition, the
RP has contexts of all clients, and access and exit of all the
clients may be managed by the RP. Compared with IP multicast,
management convenience is improved. In addition, when the upgraded
multicast router breaks down, only a unicast function provided by a
common router needs to be recovered, and a communications network
can still continually run.
A person skilled in the art should understand that the embodiments
of the present application may be provided as a method, a system,
or a computer program product. Therefore, the embodiments of the
present application may use a form of hardware only embodiments,
software only embodiments, or embodiments with a combination of
software and hardware. In addition, the embodiments of the present
application may use a form of a computer program product that is
implemented on one or more computer-usable storage media (including
but not limited to a magnetic disk storage, a CD-ROM, and an
optical memory) that include computer usable program code.
The embodiments of the present application are described with
reference to the flowcharts and/or block diagrams of the method,
the device, system, and the computer program product according to
the embodiments of the present application. It should be understood
that computer program instructions may be used to implement each
process and/or each block in the flowcharts and/or the block
diagrams, and a combination of a process and/or a block in the
flowcharts and/or the block diagrams. These computer program
instructions may be provided for a general purpose computer, a
dedicated computer, an embedded processor, or a processor of any
other programmable data processing device to generate a machine, so
that the instructions executed by a computer or a processor of any
other programmable data processing device generate an apparatus for
implementing a function in one or more processes in the flowcharts
and/or in one or more blocks in the block diagrams.
These computer program instructions may be stored in a computer
readable memory that can instruct the computer or any other
programmable data processing device to work in a manner, so that
the instructions stored in the computer readable memory generate an
artifact that includes an instruction apparatus. The instruction
apparatus implements a specified function in one or more processes
in the flowcharts and/or in one or more blocks in the block
diagrams.
These computer program instructions may also be loaded onto a
computer or another programmable data processing device, so that a
series of operations and operations are performed on the computer
or the another programmable device, thereby generating
computer-implemented processing. Therefore, the instructions
executed on the computer or the another programmable device provide
operations for implementing a function in one or more processes in
the flowcharts and/or in one or more blocks in the block
diagrams.
Obviously, a person skilled in the art can make various
modifications and variations to the embodiments of the present
application without departing from the spirit and scope of this
application. This application is intended to cover these
modifications and variations to the embodiments of the present
application provided that they fall within the scope of protection
defined by the following claims and their equivalent technologies
of this application.
* * * * *